Inventions, Volume 1, Issue 1 (March 2016) – 8 articles

In part II of this group of papers, the control of the gait of a biped robot during rectilinear walk was considered. The modeling approach and simulation, using Kane’s method with implementation leveraged by Autolev, a symbolic computational environment that is complementary, was discussed in part I. Performing turns during the walk is technically more complex than the rectilinear case and deserves further investigation. The problem is solved in the present part III as an extension of part II. The robot executes a rectilinear walk on a local reference frame whose progression axis is always tangent, and its origin performs the involute of the path curve. The curve is defined by its curvature (osculating circle) and center of curvature (evolute) along the path. Radius of curvature and center can change continuously (in practice at every sampling time). For postural equilibrium, Center of Gravity and Zero Moment Point (COG/ZMP) follow the same preview reference proposed for rectilinear walk ($co{g}_{Re{f}_x}\left(t\right),{\dot{cog}}_{Re{f}_x}\left(t\right)$, $co{g}_{Re{f}_y}\left(t\right),{\dot{cog}}_{Re{f}_y}\left(t\right)$). The effect of the turn on the sagittal plane is negligible and is ignored, while on the frontal plane it is accounted for by an offset on COG reference to compensate for the centrifugal acceleration. The body trunk and local frame rotation, and the generation of the references on this moving frame of the free foot trajectory during the swing deserve attention. Full article

This is the second part of a three-part paper. It extends to the free walking results of a previous work on postural equilibrium of a lower limb exoskeleton for rehabilitation exercises. A classical approach has been adopted to design gait (zero moment point (ZMP), linearized inverted pendulum theory, inverse kinematics obtained through the pseudo-inverse of Jacobian matrices). While several ideas exploited here can be found in other papers of the literature, e.g., whole-body coordination, our contribution is the simplicity of the whole control approach that originates logically from a common root. (1) The approximation of the unilateral foot/feet-ground contacts with non-holonomic constraints leads naturally to a modeling and control design that implements a two-phase switching system. The approach is facilitated by Kane’s method and tools as described in Part I. (2) The Jacobian matrix is used to transfer from the Cartesian to the joint space a greater number of variables for redundancy than the degrees of freedom (DOF). We call it the extended Jacobian matrix. Redundancy and the prioritization of postural tasks is approached with weighted least squares. The singularity of the kinematics when knees are fully extended is solved very simply by fake knee joint velocities. (3) Compliance with the contact and accommodation of the swing foot on an uneven ground, when switching from single to double stance, and the transfer of weight from one foot to the other in double stance are approached by exploiting force/torque expressions returned from the constraints. (4) In the center of gravity (COG)/ZMP loop for equilibrium, an extended estimator, based on the linearized inverted pendulum, is adopted to cope with external force disturbances and unmodeled dynamics. Part II treats rectilinear walking, while Part III discusses turning while walking. Full article

A biped robot is a mechanical multichain system. The peculiar features, that distinguishes this kind of robot with respect to others, e.g., industrial robots, is its switching nature between different phases, each one is the same mechanics subject to a different constraint. Moreover, because these (unilateral) constraints, represented by the contact between the foot/feet and the ground, play a fundamental role for maintaining the postural equilibrium during the gait, forces and torques returned must be continuously monitored, as they pose stringent conditions to the trajectories that the joints of the robot can safely follow. The advantages of using the Kane’s method to approach the dynamical model (models) of the system are outlined. This paper, divided in three parts, deals with a generical biped device, which can be an exoskeleton for rehabilitation or an indipendent robot. Part I is devoted to modelling and simulation, part II approaches the control of walk in a rectilinear trajectory, part III extends the results on turning while walking. In particular, this part I describes the model of the biped robot and the practicalities of building a computer simulator, leveraging on the facilities offered by the symbolic computational environment Autolev that complements the Kane’s method. Full article

Due the concern about serious environmental pollution and fossil energy consumption, introducing solar generation into ship power systems has drawn greater attention. However, the penetration of solar energy will result in ship power system instability caused by the uncertainties of the solar irradiation. Unlike on land, the power generated by photovoltaic (PV) modules on the shipboard changes as the ship rolls. In this paper, a high-speed flywheel energy storage system (FESS) is modeled to smooth the PV power fluctuations and improve the power quality on a large oil tanker which contains a PV generation system, a diesel generator, a FESS, and various types of ship loads. Furthermore, constant torque angle control method combined with sinusoidal pulse width modulation (SPWM) approach is proposed to control the FESS charging and discharging. Different ship operating situations and the impact of the ship rolling is taken into consideration. The simulation results demonstrate the high efficiency and fast response of the flywheel energy storage system to enhance the stability of the proposed hybrid ship power system. Full article

In this paper, a technique that combines digital image correlation and wire electrical discharge machining for the measurement of the residual strain is presented. The significant potential benefits of this work include noncontact, high-speed, and online measurement. A ring-core-based groove in the surface of the specimen is cut to release the residual stresses present inside the core. The deformation due to these stresses can be measured by digital image correlation to measure the relieved strains. Moreover, the sizes of the reference areas on the specimens and the tracks of these areas after wire electrical discharge machining are investigated. The proposed method is applied to six different specimens to characterize their relieved strains. Full article

In this study, high-density single crystalline Ga-doped ZnO (GZO) nanorods were grown on glass substrate by the hydrothermal method. The structural and optoelectronic properties of Ga-doped ZnO nanorods were studied. The microstructure of the GZO was studied by scanning electrical microscope (SEM). The structural characteristics of the GZO were measured by X-ray diffraction (XRD). It was found that the peaks related to the wurtzite structure ZnO (100), (002), and (101) diffraction peaks. The (002) peak indicates that the nanorods were preferentially oriented in the c-axis direction. The existence of Ga was examined by energy diffraction spectra (EDS), indicating the Ga atom entered into the ZnO lattice. The optical properties of the GZO were measured by photoluminescence spectra. It was found that all GZO nanorod arrays showed two different emissions, including UV (ultraviolet) and green emissions. GZO nanorod metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors (PD) were also fabricated. The photo-current and dark-current constant ratio of the fabricated PD was approximately 15.2 when biased at 1 V. Full article

This study integrated the techniques of the high-performance heat transfer and thermoelectric conversion to build a thermoelectric generator system installed at the exhaust pipe of a real single-cylinder and four-stroke engine of 35.8 c.c. displacement. This system was made of the heat absorber, thermoelectric generator modules and the external heat sink. The pin-fin array was inserted into the circuitous duct to form the heat absorber, which could increase the heat-exchange surface area and the heat-exchange time to reach the object of absorbing heat and increasing thermoelectric conversion effectively. Full article

Scholars from academic units and research personnel from company research departments are welcome to contribute research papers which are innovative and inventive to the journal Inventions, the founding of which has been embodied with three very important aims: The first is the timely publication, spread and promotion of innovative and inventive research papers. [...] Full article